Series of Stable Anionic Lanthanide Metal–Organic Frameworks as a Platform for Pollutant Separation and Efficient Nanoparticle Catalysis

Abstract

Eight new stable porous lanthanide metal–organic frameworks (Ln-OFs), namely, [Ln2(BPTC)2]­[(CH3)2NH2]2 [Ln = Ho (1), Eu (2), Gd (3), Dy (4), Er (5), Tm (6), Yb (7), Lu (8)], were prepared by 3,3′,5,5′-biphenyltetracarboxylic acid (H4BPTC) and lanthanide ions by solvothermal reactions. Complexes 1–8 show a three-dimensional (3D) 6,6-connected network {412·63}·{48·66·8} topology based on binuclear (Ln2) clusters and feature a one-dimensional curving porous channel occupied by exchangeable dimethylamine cations ([(CH3)2NH2]+) in the 3D anionic frameworks. The occupied [(CH3)2NH2]+ in the anionic channels exhibited excellent ion-exchange ability, which is favorable to Pd2+ and cationic dye adsorption. Consequently, 1–8 were used to load Pd nanoparticles to catalyze the reduction of nitrophenols and adsorb and desorb methyl blue (MB). The catalytic reaction efficiencies of Pd@1–8 were higher than that of Pd/C (5 wt %) in the hydrogenation reaction of p-nitrophenol (p-NP). Moreover, Pd@1 exhibited good cycle stability and achieved nearly 100% p-NP conversion after eight cycles. Meanwhile, compound 1 also exhibited a high adsorption ability of MB, possessing an adsorption capacity of 1.41 g·g–1 (second only to 1.49 g·g–1 reported in the literature) selectively over rhodamine B (RhB) and methyl orange (MO) in aqueous solutions. Remarkably, the skeleton of 1 remained stable after four adsorption–desorption cycles of MB in aqueous solution.

Series of TM-OFs as a Platform for Efficient Catalysis and Multifunctional Luminescence Sensing

“…The chemical stabilities of 1 – 3 were investigated in aqueous solutions with different pH values (pH 2–12). The test method for chemical stability was consistent with that in our previously published work . The measured PXRD patterns indicated that the framework and crystallinity of complexes 1 and 2 did not change after immersion, which proved that they had excellent chemical stability (Figure ).…”

“…In the presence of Pd@ 1 involved in the reaction, the absorbance of nitrophenols gradually decreased together with new absorption peaks corresponding to the product of aminophenols. The reaction efficiency constants of the catalytic reactions were calculated by a pseudo-first-order kinetic model …”

“…The test method for chemical stability was consistent with that in our previously published work. 7 The measured PXRD patterns indicated that the framework and crystallinity of complexes 1 and 2 did not change after immersion, which proved that they had excellent chemical stability (Figure 3). However, 3 exhibited poor stability in the aqueous phase, which may be caused by the longer Cd−O bond lengths in 3.…”

“…The reaction efficiency constants of the catalytic reactions were calculated by a pseudo-first-order kinetic model. 7 The catalyst Pd@1 catalyzed the complete reduction of nitrophenols in 4.5 (4-NP), 3.5 (2-NP), and 1.5 (3-NP) min, respectively, which corresponds to catalytic conversions of 100%, 97%, and 98%, respectively. This fact indicates that Pd@ 1 exhibits excellent catalytic reduction efficiencies for these nitrophenols.…”

“…Highly dispersed ultrafine noble-metal nanoparticles (MNPs) have attracted a great deal of attention from researchers in the hydrogenation reduction of nitro compounds. Among the various noble-metal MNPs, Pd NPs show excellent catalytic capabilities. , However, the size of Pd NPs is hard to control during catalytic reactions; free small-sized Pd NPs with high surface energy tend to aggregate into larger particles, resulting in a reduction of their catalytic activity. In order to reduce the particle size of Pd NPs, scientists need to synthesize porous materials with appropriate pore sizes to load Pd NPs to improve their catalytic activity.…”